With the development of multiple air interface standards in mobile wireless, there is an increasing need for devices to support several air interface modes, e.g., Global System for Mobile Communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), 1x Radio Transmission Technology (1xRTT), Evolution-Data Optimized (EvDO) for High Rate Packet Data (HRPD) service and Evolved HRPD (eHRPD) service, Long Term Evolution (LTE) for Universal Mobile Telecommunications System Terrestrial Radio Access (UTRA) service or Evolved UTRA (eUTRA). At the same time the need for accurate device position determination in mobile wireless is growing. Position determination requires the device to take radio measurements. The radio could be a Global Positioning System (GPS) radio and a radio for one of the previously mentioned air interfaces. The position determination could be done by the device itself, with the assistance of a server or by a server with the measurements provided by the device to the server.
Generally speaking, mobile devices operate (both receive and transmit) in only one mode at a time, i.e., using only one interface at a time. Consequently, it follows that the mode that the device is operating in at any one time will be the preferred mode for taking air interface measurements and performing the position determination. This assumes that the position determination technology can make use of the measurements from that particular air interface. This may not always be the case.
For example, in a multi-mode device that supports both 4G and 3G air interfaces, e.g., LTE, EvDO (for eHRPD and HRPD services) and 1xRTT, positioning technologies exist for 1xRTT measurements and are being developed for LTE. Technologies do not exist nor are they being planned for EvDO. Note that with the convergence of voice and data and the need for higher capacity propelling, operators go to Voice over IP so that all services can work simultaneously. The problem is particularly acute for E911 (Emergency 911) where positioning accuracy is mandated by the Federal Communications Commission (FCC).